Halloween Haunt Hack

This is a pretty quick hack to trigger sound and lightning flashes for a simple Halloween Haunt. It uses a light dependent resister to detect a shadow passing over the sensor. An Arduino reads the sensor and triggers a sound to be played and simulates lightning by flashing a bright LED. The sound is played from a Radio Shack digital recording module.A

Step 1: Video Tour

Step 2: The Code

// Lightning
//
// Credits to Rob Tillaart for the lightning simulation code. I don't remember now
// in which forum I (Google) found this code but I think the timing is spot on.
//
// I expanded on the lightning code to trigger a hacked Radio Shack recording module
// when a photo resistor detects darkness below threshold. Hey, it's a cheap form of
// motion detection for a Halloween prop.
//
// Credits to David A Mellis
// and Tom Igoe for the sensor calibration public domain code at
// http://arduino.cc/en/Tutorial/Calibration
//
//
#define BETWEEN 2579
#define DURATION 43
#define TIMES 7

#define SENSORPIN A0
#define TRIGGERPIN 7
#define FLASHPIN 13

unsigned long lastTime = 0;
unsigned long triggerTime = 0;
int waitTime = 0;
int sensorValue = 0;
boolean lightning = false;

int sensorMin = 1023;        // minimum sensor value
int sensorMax = 0;           // maximum sensor value
int sensorThreshold = 0;

void setup()
{
  Serial.begin(115200);
  Serial.println("lightning 0.0");

  pinMode(FLASHPIN, OUTPUT);
  pinMode(TRIGGERPIN, OUTPUT);
  pinMode(SENSORPIN, INPUT);
  delay(1000);

  // Calibrate
  // 
  // Sensor readings during the first five seconds of the sketch
  // execution define the minimum and maximum of expected values
  // attached to the sensor pin.
  // This allows the circuit to be used in a variety of lighting conditions
  // by exposing the sensor to the brightest and darkest values to be seen
  // from it's resting position.
  //
  while (millis() < 5000) {
    sensorValue = analogRead(SENSORPIN);

    // record the maximum sensor value
    if (sensorValue > sensorMax) {
      sensorMax = sensorValue;
    }

    // record the minimum sensor value
    if (sensorValue < sensorMin) {
      sensorMin = sensorValue;
    }
  }
}

void loop()
{
  if (millis() - triggerTime > 15000) {
    sensorValue = analogRead(SENSORPIN);
    // apply the calibration to the sensor reading
    // sensorValue = map(sensorValue, sensorMin, sensorMax, 0, 255);
    Serial.println(sensorMin);
    Serial.println(sensorMax);
    Serial.println(sensorThreshold);
    Serial.print("Sensor value: ");
    Serial.println(sensorValue);
    sensorThreshold = (sensorMax - sensorMin) * 2 / 3;
    if (sensorValue < sensorThreshold) {
      digitalWrite(TRIGGERPIN, HIGH);
      triggerTime = millis();
      delay(500);
      digitalWrite(TRIGGERPIN, LOW);
      lightning = true;
    }
    else
    {
      lightning = false;
    }
  }
  if (millis() - waitTime > lastTime)  // time for a new flash
  {
    // adjust timing params
    lastTime += waitTime;
    waitTime = random(BETWEEN);

    for (int i=0; i< random(TIMES); i++)
    {
      // Serial.println(millis());
      if (lightning)
        digitalWrite(FLASHPIN, HIGH);
      delay(20 + random(DURATION));
      digitalWrite(FLASHPIN, LOW);
      delay(10);
    }
  }

  // do other stuff here

}